1. Field of the Invention
This invention relates to a video system and more particularly to a video system which is capable of looking up at a high speed a video signal recorded on a recording medium having a large capacity.
2. Description of the Related Art
The recent advancement of technology for recording at a high degree of density has come to enable a VTR to perform long-time recording on a video tape. For example, the VTR of the VHS standards has become capable of recording a video signal over a period of eight hours. As a result of this, a high speed look-up system has become necessary. To meet that requirement, there have been proposed look-up systems called VISS (a VHS index search system) and a VASS (VHS address search system) which are operating on the basis of a so-called CTL coding technique. In the CTL coding, the width (or duty ratio, to be exact) of control signals to be recorded on a video tape is arranged to have two different widths. The wider control signal is defined by the binary value of "0" and the narrower control signal by another binary value of "1". Digital signals are recorded by combining the values "0" and "1". Then, these digital signals are used for a look-up operation. In accordance with the VISS system, index codes which serve like the indices of books are marked in desired parts of the video tape. In reproduction, a look-up action is first performed either at a high speed or automatically for the leader part of a desired record before the record is reproduced in an ordinary manner. In the VASS system, address codes (address information) are marked in figures of four places beforehand and the leader part of a desired record is automatically looked up with reference to the four-place figures before reproduction.
The recording medium which permits recording many video signals or a long-time video signal is not limited to a video tape but may be selected from among other media such as an optical disc, an opto-magnetic disc, etc. which have already been developed into a practicable state. Further, the adoption of a vertical magnetizing method for high density recording has made possible long-time video recording on a magnetic disc.
By virtue of the above stated VISS or VASS system, the look-up capability of the VTR on a video tape has been greatly enhanced. However, with respect to easy and rapid confirmation of images recorded on a video tape, the look-up capability of the VTR is still insufficient. Further, since the market prices of video tapes have recently lowered to a great degree, each home is regarded as having a considerable number of tapes. In other words, the conventional look-up system is incapable of permitting the operator to easily and promptly know what kind of image is recorded on the video tape.
Such high speed look-up becomes necessary in cases where many images are recorded on an optical disc, an opto-magnetic disc, a magnetic disc of a large capacity or the like. In an apparatus, such as VTR editing system, that is arranged to have identification (ID) signals of varied kinds additionally recorded along with a video signal on the recording medium and to reproduce images in a desired sequence by using the recorded ID signals, a reproducing VTR and a recording VTR are controlled on the basis of a time code recorded on the video tape. The control parameters of the system are temporarily stored in a floppy disc or the like by means of a data recorder called a logging device to ensure the reproducibility of the details of control thereof.
In addition to the above stated system, a VTR having a special automatic reproducing function has been disclosed in Japanese Patent Application SHO 59-120963. This VTR is arranged to record control information in the form of a cue signal. The VTR disclosed facilitates data management despite having a simple structural arrangement. However, it is hardly suited for cases wherein complex operation control or a display of the contents of the record, etc. is required.
In the above stated conventional system, wherein the sequence of reproducing procedures is controlled in accordance with a program, it has been difficult to carry out a complex operation such as a loop action for slowly reproducing the record of a specific section an N number of times and to have the tape rewound to an extent corresponding to an M number of frames. It is also a problem with the prior art described that, in case where control data is to be stored in a floppy disc, the control data alone hardly enables the operator to grasp in outline the contents of the whole tape.